Agricultural machinery is commonly used by farmers, crop growers and others to improve the efficiency of planting and harvesting crops. Some crops are grown with the aid of irrigation systems, such as trickle irrigation, and plastic sheeting known as plastic mulch, which are at least partially embedded in the ground at the start of the growing period. Plastic mulch provides a range of benefits including helping modulate soil temperature, reduce soil erosion, evaporation, fertilizer leaching and weed problems and increase produce quality and yields. When the crops are harvested, the plastic mulch and often the irrigation system need to be removed from the ground for disposal. Plastic mulch retrievers are agricultural machines designed for this purpose and are typically drawn behind a powered vehicle, such as a tractor. Plastic mulch retrievers are available in a range of designs, the main features of which will now be discussed.
One known plastic mulch retriever comprises a pair of coulter wheels at a front end, which cut into the ground and plant matter, such as roots. A pair of angled, substantially horizontal blades mounted rearward of the coulter wheels also cut into the ground and underneath the plastic mulch embedded in the ground. As the mulch retriever is pulled along behind the powered vehicle, the mulch is unearthed and left lying loosely on top of the planting bed. A centre coulter wheel rearward of the pair of coulter wheels slices the plastic mulch into two halves. The positions of the coulter wheels are adjustable to accommodate different size planting beds. One drawback of this mulch retriever is that the unearthed mulch needs to be collected for disposal, which is labour intensive and inefficient because the unearthed mulch remains strewn along the growing area.
A modification to the aforementioned mulch retriever comprises a plurality of propane burners rearward of the coulter wheels and angled blades. The burners incinerate the unearthed mulch thus avoiding the need to collect the unearthed mulch. However, incineration is environmentally unfriendly and illegal in some jurisdictions. The burners also require a propane tank, which adds to the both the financial and environmental cost.
In another plastic mulch retriever design, the unearthed mulch is rolled onto a pair of aligned, rotating rollers rotatably mounted toward a rear of the mulch retriever on a pair of longitudinal arms. An operator stands on a platform to control the speed of rotation of the rollers to be commensurate with the speed of the powered vehicle and the rate at which the mulch is being unearthed. Once all of the mulch has been retrieved or the rollers are full, each arm comprising one of the respective rollers is swung outwardly and the rollers separate about a substantially central point allowing the retrieved mulch bundle wrapped around the rollers to fall to the floor for disposal.
Whilst the aforementioned plastic mulch retriever is effective at retrieving the embedded mulch, one problem that is experienced is the plastic mulch retains a lot of soil, roots, debris and the like. It is desirable to minimize the amount of earth removed during plastic mulch retrieval to minimize the amount of nutrients removed from the soil. The earth attached to the removed mulch also adds to the weight of the bundle for disposal. Furthermore, the capacity of the rollers for capturing the plastic mulch is reduced because the attached earth occupies some of the volume. It will be appreciated that clods of earth, debris and the like occupy significantly more volume than plastic sheeting. Therefore, efficiency is affected because more stops must be made to empty the rollers than would otherwise be necessary.